The invention herein described was made in the course of or under a contract thereunder with the United States Air Force Systems Command.
This invention relates to the preparation of Binor-S. More particularly, the invention relates to the preparation of Binor-S from norbornadiene. Still more particularly, the invention relates to the dimerization of norbornadiene to Binor-S.
Binor-S, upon further processing, for example, hydrogenation, can be converted into a component of a high energy fuel which can be used in either jet or rocket propulsion. Jet propulsion includes a jet engine which can be used for a missile plane and others and includes the three basic types, i.e., ramjet, turbo-jet and pulse jet. The term jet generally refers to a device containing its own oxygen or oxidizing agent.
Binor-S is known by the systematic chemical name of endo-cis-endo-heptacyclo (5.3.1.1.sup.2,6 .1.sup.4,12 .1.sup.9,11 .0.sup.3,5 .0.sup.8,10)-tetradecane. Its melting point is about 65.degree. C.
Preparation of Binor-S is disclosed in an article in the Journal of the American Chemical Society, [88:22] Nov. 5, 1966, pages 4890-4894. The article is titled ".pi.-Complex Multicenter Reactions Promoted by Binuclear Catalysts Systems. "Binor-S", a New Heptacyclotetradicane via Stereospecific Dimerization of Bicycloheptadiene", by G. N. Schrauzer, et al. Disclosed is the dimerization of bycycloheptadiene (also known as norbornadiene) to Binor-S using metal salts of cobalt carbonyl hydrides (e.g., Zn(Co(CO).sub.4).sub.2). A Lewis acid, such as AlBr.sub.3, can be used as a cocatalyst with the transistion metal carbonyl catalyst. Another related article appears in Tetrahedron Letters, No. 8, 1970, pages 543-545 titled "New Catalysts of Stereospecific Norbornadiene Dimerization to "Binor-S", by G. N. Schrauzer et al. This second article discloses the use of RhCl[P(C.sub.6 H.sub.5).sub.3 ].sub.3 as a catalyst with BF.sub.3 O(C.sub.2 H.sub.5).sub.2 as a cocatalyst for the dimerization of norbornadiene to Binor-S.
A metal-cobalt carbonyl complex useful as a catalyst in the polymerization of norbornadiene is disclosed in U.S. Pat. No. 3,679,722. Also, U.S. Pat. No. 3,676,474 discloses a multinuclear .pi.-complex having at least two metal cobalt bonds which can be used as a catalyst in the dimerization of norbornadiene.
Norbornadiene is also known as bicyclo(2.2.1) heptadiene-2,5. A method of preparation is disclosed in U.S. Pat. No. 2,875,256 issued Feb. 24, 1959. Norbornadiene will be referred to as NBD hereinafter. NBD can be represented by either one of the following structural formulas: ##STR1##
During the dimerization of NBD more than one dimer is possible. G. N. Schrauzer, in his review "On Transition Metal-Catalyzed Reactions of Norbornadiene and the Concept of a Complex Multicenter Processes" in Advances on catalysis 18, 373 (1968) Acad. Press, describes the fourteen theoretically possible dimers of NBD. The possible dimers, grouped according to the number of their carbocyclic rings, are as shown in accompanying Table I. Any and each of the dimers shown in Table I have different physical and chemical properties.
Thus, a specific synthesis problem in the dimerization of NBD, as can be visualized from the number of possible isomers, is to obtain both excellent selectivity and conversion to a desired isomer.